scholarly journals A Sequence of Phase Transformations and Phases in NiCoFeCrGa High Entropy Alloy

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1076
Author(s):  
Ádám Vida ◽  
János Lábár ◽  
Zoltán Dankházi ◽  
Zsolt Maksa ◽  
Dávid Molnár ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
High Entropy ◽  
Transmission Electron ◽  
Temperature Ranges ◽  
Face Centered ◽  
Electron Energy Loss

The present investigation is directed to phase transitions in the equimolar NiCoFeCrGa high entropy alloy, which is a mixture of face-centered cubic (FCC) and body-centered cubic (BCC) crystalline phases. The microstructure of the samples was investigated by using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), transmission electron microscopy-based energy-dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS), as well as X-ray diffraction (XRD) measurements. Based on the phases observed in different temperature ranges, a sequence of the phase transitions can be established, showing that in a realistic process, when freely cooling the sample with the furnace from high to room temperature, a microstructure having spinodal-like decomposition can also be expected. The elemental mapping and magnetic behaviors of this decomposed structure are also studied.

Structural, morphological, and magnetic study of nanocrystalline cobalt-copper powders synthesized by the polyol process

1995 ◽  
Vol 10 (6) ◽  
pp. 1546-1554 ◽  
Author(s):  
G.M. Chow ◽  
L.K. Kurihara ◽  
K.M. Kemner ◽  
P.E. Schoen ◽  
W.T. Elam ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Copper Powders ◽  
Face Centered ◽  
Increasing Temperature ◽  
X Ray Absorption

Nanocrystalline CoxCu100−x (4 ⋚ x ⋚ 49 at. %) powders were prepared by the reduction of metal acetates in a polyol. The structure of powders was characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), extended x-ray absorption fine structure (EXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, and vibrating sample magnetometry (VSM). As-synthesized powders were composites consisting of nanoscale crystallites of face-centered cubic (fcc) Cu and metastable face-centered cubic (fcc) Co. Complementary results of XRD, HRTEM, EXAFS, NMR, and VSM confirmed that there was no metastable alloying between Co and Cu. The NMR data also revealed that there was some hexagonal-closed-packed (hcp) Co in the samples. The powders were agglomerated, and consisted of aggregates of nanoscale crystallites of Co and Cu. Upon annealing, the powders with low Co contents showed an increase in both saturation magnetization and coercivity with increasing temperature. The results suggested that during preparation the nucleation of Cu occurred first, and the Cu crystallites served as nuclei for the formation of Co.

scholarly journals Development of Ternary and Quaternary Catalysts for the Electrooxidation of Glycerol

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
L. M. Artem ◽  
D. M. Santos ◽  
A. R. De Andrade ◽  
K. B. Kokoh ◽  
J. Ribeiro
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cyclic Voltammetry ◽  
Pechini Method ◽  
Particle Sizes ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Face Centered

This work consisted in the preparation of platinum-based catalysts supported on carbon (Vulcan XC-72) and investigation of their physicochemical and electrochemical properties. Catalysts of the C/Pt-Ni-Sn-Me (Me = Ru or Ir) type were prepared by the Pechini method at temperature of350∘C. Four different compositions were homemade: C/Pt60Sn10Ni30, C/Pt60Sn10Ni20Ru10, C/Pt60Sn10Ni10Ru20, and C/Pt60Sn10Ni10Ir20. These catalysts were electrochemically and physically characterized by cyclic voltammetry (CV), chronoamperometry (CA) in the presence of glycerol 1.0 mol dm-3, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). XRD results showed the main peaks of face-centered cubic Pt. The particle sizes obtained from XRD and HRTEM experiments were close to values ranging from 3 to 8.5 nm. The CV results indicate behavior typical of Pt-based catalysts in acid medium. The CV and CA data reveal that quaternary catalysts present the highest current density for the electrooxidation of glycerol.

Transmission Electron Microscopy Studies of the Nanoscale Structure and Chemistry of Pt50Ru50 Electrocatalysts

2002 ◽  
Vol 8 (1) ◽  
pp. 50-57 ◽  
Author(s):  
Rhonda M. Stroud ◽  
Jeffrey W. Long ◽  
Karen E. Swider-Lyons ◽  
Debra R. Rolison
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Face Centered Cubic ◽  
Oxidation Activity ◽  
Transmission Electron ◽  
Diffraction Lattice ◽  
Nanoscale Structure ◽  
Face Centered ◽  
Electron Energy Loss ◽  
Lower Oxidation

The structural and chemical heterogeneity of 2.5-nm Pt50Ru50 electrocatalysts was studied by transmission electron microscopy using selected area diffraction, lattice imaging, electron-energy loss spectroscopy, and energy-dispersive X-ray spectroscopy. The catalysts with the highest methanol oxidation activities exhibit oxidation-induced phase separation on the nanoscale to form Pt-rich metal embedded in Ru-rich hydrous and anhydrous oxide. Reduction of the oxide-on-metal samples produces a true bimetallic face-centered cubic Pt50Ru50 alloy, with 275 times lower oxidation activity.

Synthesis of Well-Dispersed Copper Nanoparticles by L-Ascorbic Acid in Diethyleneglycol

2012 ◽  
Vol 549 ◽  
pp. 378-381 ◽  
Author(s):  
Jun Cheng Zhou ◽  
Wei He ◽  
Yao Tang ◽  
Yong Suan Hu
Keyword(s):  
Electron Microscopy ◽  
Ascorbic Acid ◽  
Copper Nanoparticles ◽  
Metallic Copper ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Copper Particles ◽  
Transmission Electron ◽  
Face Centered ◽  
Fcc Structure

Metallic copper nanoparticles were synthesized in the presence of poly(N-vinylpyrrolidone) (PVP) as the capping agent and L-ascorbic acid as the reducing agent in diethyleneglycol (DEG) solvent. The obtained copper nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The EDS and XRD results showed that the resultant particles were confirmed to be crystalline Cu with a face-centered cubic (fcc) structure. It was also observed that the diameter of obtained copper particles ranging from 80 to 120nm via SEM and TEM.

ENHANCED GAS SENSING PROPERTIES OF p-TYPE TeO2 NANORODS FUNCTIONALIZED WITH Pd

NANO ◽  
2011 ◽  
Vol 06 (05) ◽  
pp. 455-460 ◽  
Author(s):  
HYUNSU KIM ◽  
SUNGHOON PARK ◽  
CHANGHYUN JIN ◽  
CHONGMU LEE
Keyword(s):  
Electron Microscopy ◽  
Gas Sensing ◽  
Average Diameter ◽  
Pd Nanoparticles ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Sensing Properties ◽  
Transmission Electron ◽  
Face Centered ◽  
P Type

TeO2 nanorods functionalized with Pd were prepared by a three-step process comprising thermal evaporation of Te powders, Pd deposition by photo-reduction, and annealing. Sensors were fabricated by using the Pd -functionalized TeO2 nanorods. Scanning electron microscopy images exhibited that the nanorods with diameters in a range of 50–100 nm and lengths of a few micrometers were covered with the Pd nanoparticles with an average diameter of ~ 15 nm. Transmission electron microscopy and X-ray diffraction analysis revealed that the nanorods were monocrystalline simple tetragonal TeO2 . On the other hand, the nanoparticles on them were confirmed to be nanocrystalline face-centered cubic Pd . The multiple-networked TeO2 nanorod sensors exhibited a sensitivity of 3.13% at 100 ppm NO2 at 300°C, whereas the Pd -functionalized TeO2 nanorod sensors exhibited a sensitivity of 11.97% under the same condition. The recovery time of TeO2 nanorods was decreased considerably at every NO2 concentration by the Pd -functionalization even if the response time decreased or increased slightly depending upon the NO2 concentration. In addition, the origin of the enhancement of the sensing properties of the TeO2 nanorods by functionalization with Pd is discussed.

Influence of High-Pressure Torsion on the Microstructure and the Hardness of a Ti-Rich High-Entropy Alloy

2016 ◽  
Vol 879 ◽  
pp. 732-737 ◽  
Author(s):  
Anita Heczel ◽  
Lola Lilensten ◽  
Julie Bourgon ◽  
Loic Perrière ◽  
Jean Philippe Couzine ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
High Pressure ◽  
High Pressure Torsion ◽  
High Entropy Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Entropy ◽  
Transmission Electron ◽  
Bcc Structure

High-Pressure Torsion (HPT) is one of the most effective severe plastic deformation techniques in grain refinement. The goal of this study was to investigate the influence of HPT on the microstructure and hardness of a Ti-rich High-Entropy Alloy (HEA). The evolution of the grain size due to 1 turn of HPT was studied by transmission electron microscopy. Besides the refinement of the microstructure, a phase transition also occurred during HPT, as revealed by X-ray diffraction. The initial bcc structure transformed into a martensitic phase throughout the material. The features of this phase transformation were studied on a sample compressed to low strain values. The hardness as a function of the distance from the center in the HPT-processed disk was measured and correlated to the microstructure.

Characterization of Reactively Sputtered Titanium Carbide Films by Analytical Electron Microscopy

1985 ◽  
Vol 62 ◽  
Author(s):  
J. Tafto ◽  
G. Rajeswaran ◽  
T. Saulys
Keyword(s):  
Electron Microscopy ◽  
Core Loss ◽  
Analytical Electron Microscopy ◽  
Face Centered Cubic ◽  
Transmission Electron ◽  
Partial Pressures ◽  
The Face ◽  
Face Centered ◽  
Electron Energy Loss

ABSTRACTTICx films prepared by reactive sputtering using a Ti target and different methane partial pressures were characterized by analytical transmission electron microscopy. The films are polycrystalline, and the plasmon energy increases considerably with increasing carbon content. Combination of the information obtained from electron energy loss plasmon and core loss spectra, and electron diffraction indicates that x in TiCx increases linearly with methane partial pressure. We find that the face centered cubic TIC phase spans the composition from TiC0.2 to TiC1.0 and when x<l we have a mixture of TiC1.0 and amorphous C.

High photoelectric PPV/PVA/Ag composite nanofibers by co-electrospinning

2015 ◽  
Vol 35 (7) ◽  
pp. 689-697 ◽  
Author(s):  
Yang Gao ◽  
Zhiyao Sun ◽  
Liguo Sun ◽  
Cheng Wang ◽  
Shuhong Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Composite Nanofibers ◽  
Average Diameter ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Ag Nps ◽  
Photoelectric Properties ◽  
Transmission Electron ◽  
Face Centered ◽  
Xrd Patterns

Abstract Poly(phenylene vinylene)/polyvinyl alcohol/Ag (PPV/PVA/Ag) composite nanofibers with excellent photoelectric properties were prepared by coaxial electrospinning using PPV/PVA as the shell and Ag nanoparticles (NPs) as the core, Ag NPs aqueous solution was prepared by the reduction method. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Ag NPs are of a face-centered cubic structure, with an average diameter of 46 nm and the composite nanofibers have uniform and continuous morphology. With increasing Ag content, the diameters of the composite nanofibers decreased from 653 nm to 250 nm. The X-ray diffraction (XRD) patterns verified that in the composite nanofibers, the Ag NPs are not transformed. In the photoluminescence spectra, the PPV/PVA/Ag composite nanofibers presented red-shift compared with PPV/PVA nanofibers. Under illumination, the as-prepared PPV/PVA/Ag composite nanofibers exhibited relatively high photocurrent intensity.

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